The long term goals of the proposed studies are a) to determine factors which influence the expression of handedness in primates and b) to examine the reproductive and immunological correlates of behavioral lateralization in primates. The specific aims are a) to assess environmental and genetic factors as determinants of hand preference b) to determine whether measures of developmental stability can explain individual differences in phenotypic expressions of hand preference and c) to determine whether handedness is predictive of compromised immunological functioning and/or reproductive biology. The role of genetic and environmental factors on the expression of hand preference will be determined by comparing the concordance in hand preference in parent/offspring dyads who were either conspecific-reared or cross-fostered. Measures of fluctuating asymmetry (FA), specifically dermatoglyphics, will be used to assess developmental instability in the chimpanzees. The FA data will be used to determine whether chimpanzees who do not show the predicted phenotypic expression of hand preference have larger FA than comparison subjects. Larger FA values would reflect a greater effect of prenatal perturbations in certain hand preference groups. Finally, the relationship between hand preference and immunological functioning and reproductive biology will be assessed in left-, ambidextrous and right-handed chimpanzees matched on age and rearing history. These data will provide valuable information on whether non-right-handedness is associated with increased risks for health related problems and potentially reflects decreased survival fitness.